Tunable bandgaps in an elastic meta-plate with shape memory alloy springs

In this paper, a tunable metamaterial based on shape memory alloy springs is designed, which can achieve bandgap tuning by spring's unique shape memory effect. The variation mechanism of shear modulus and geometrical parameters of shape memory alloy springs is investigated by considering a detailed phase transition mechanism. For any specific temperatures, the energy band structure and frequency response spectrum of the metamaterial are calculated by numerical simulation. And the theoretical prediction models of bandgap boundary frequency and tuning range at different temperatures are established. The experimental test of vibration transmission of metamaterial is finally presented. The results show that (1) By varying the spring's shear modulus and height, the metamaterial exhibits excellent vibration isolation characteristics and bandgap tuning in low-frequency range of 124–226Hz. (2) The bandgap boundaries and tuning ranges can be predicted by the theoretical prediction model, which shows good agreement with both the simulation results and the experimental data. (3) By artificially designing shape memory alloy springs with larger shear modulus and wire radius, smaller helix radius and number of turns, the bandgap moves to higher frequencies. The current work can provide a reference for further engineering applications with the tunable elastic/acoustic metamaterials.